Just what is it about Lembit Opik? The 44-year-old Lib-Dem MP has just appeared in public with his fabulous new squeeze, 21-year-old former Wonderbra model Katie Green.

She has dark eyes, flowing locks and a figure to die for. She claims to prefer older men and says: 'It's refreshing that he sees me as intelligent.'

Search the web and you'll quickly find more pictures of this lissom lady. In most, she appears wearing precious little and not exactly in the poses I'd have recommended to anyone wishing to be admired for their intellect.

But then Lembit has a fine track record when it comes to escorting beautiful women. His last one came as a double: Gabriela Irimia, one half of the Transylvanian pop duo the Cheeky Girls.

And before that, it was redheaded Welsh weather girl Sian Lloyd. She says she was wooed by Lembit's 'surprisingly gentle handshake', although more recently she described him as 'a drunken, shambolic, tight-fisted show-off with hideous clothes'.

Now, I've known Lembit for years. We were colleagues in the Commons and I confess to really quite liking him. The combination of a Belfast accent, a Welsh constituency and an Estonian background makes him intriguing.

He's also engaging, affable and fun-loving, worlds apart from the turgid drones who inhabit the Palace of Westminster.

Unfortunately, he's not quite in Robert Redford's league. Which begs the question: how DOES he do it?

The clue lies in Sian Lloyd's revelations. Night after night, she said, she would drive him to meetings with the Lib-Dems, who were choosing their next leader. He expected it would be him - and that he would go on to become Prime Minister.

Lembit, it seems, was playing the role of the man of power. And power, believe me, is an aphrodisiac of the very strongest sort..

Lembit's probably spinning the same tale of power and destiny to sweet young Katie that he spun to Cheeky Girl Gabriela Irimia.

I'll bet he's telling her about how, after the general election, his party will turn to him as a consummate media star and beg him to lead them in coalition with the Tories - something he'll agree to on the condition he can have Chequers as his main residence.

'Would you fancy living with an important chap in a stately home, my darling?' is probably what he's saying.

Of course, Lembit wouldn't be the first to try this kind of chatup line. After all, power is extremely attractive to women.

The idea that your beau could be chatting to the Queen tomorrow and is on matey terms with the PM - and could even, given a fair wind, be the Prime Minister himself - is a heady brew for many attractive girls.

Indeed, the Commons has always been full of doe-eyed female researchers and interns who would do anything for some overweight MP in the hope of a little reflected glory. The chat-up line 'Would you like to come up and see my statutory instruments?' might not sound effective, but believe me, it really is.

The MP's wife never understands him, of course. His emotional needs are not being met. The sacrifices he makes for the country, for the cause, are not appreciated.

But you, Emma/Louise/Charlotte/Tracey, you understand, you are wonderful, and you can make him an even greater man.

It works every time. I remember watching one such pretty girl who had just landed her MP - she even managed to become his second wife.

Wearing a posh fur coat - a present from him, perhaps - she hung on his arm in the Members' Lobby, looking adoringly into his face. He was short, tubby and a bit dim, but his smile betrayed the truth: this cat had got the cream.

As she gazed at him, smitten, I wondered whether it would be kinder to warn her that he was only a jumped-up little estate agent, not at all the glamorous figure of her imagination. But it was too late for her. She had been seduced, blinded by the aura of power.

Of course, if they are heading for the dizzy heights of real power, men have to be careful about who they attract.

I was certain, for example, that John Major would be in the frame when Margaret Thatcher retired, whenever that would be. He had made many friends and no enemies since his arrival in the Commons, he had a safe seat, and he was a pleasant, even kindly man. And he also had his eyes on the country's top job.

Ironically, on this occasion, it wasn't that which attracted me to him. I suppose I had some power of my own in those days. No, our relationship was based on a friendship, a closeness.

But that is the exception rather than the rule. It's pure, intoxicating power that makes otherwise unprepossessing politicians irresistible.